Optimizer hints should be applied on Top level query as much as possible

I've experienced this issue in our app, some hints only works on Top
level query (e.g. `MAX_EXECUTION_TIME`).

2 files changed, 16 insertions, 0 deletions

diff --git a/activerecord/test/cases/adapters/mysql2/optimizer_hints_test.rb b/activerecord/test/cases/adapters/mysql2/optimizer_hints_test.rb
index b9794c5710..628802b216 100644
--- a/activerecord/test/cases/adapters/mysql2/optimizer_hints_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/optimizer_hints_test.rb
@@ -15,6 +15,14 @@ if supports_optimizer_hints?
       end
     end
 
+    def test_optimizer_hints_with_count_subquery
+      assert_sql(%r{\ASELECT /\*\+ NO_RANGE_OPTIMIZATION\(posts index_posts_on_author_id\) \*/}) do
+        posts = Post.optimizer_hints("NO_RANGE_OPTIMIZATION(posts index_posts_on_author_id)")
+        posts = posts.select(:id).where(author_id: [0, 1]).limit(5)
+        assert_equal 5, posts.count
+      end
+    end
+
     def test_optimizer_hints_is_sanitized
       assert_sql(%r{\ASELECT /\*\+ NO_RANGE_OPTIMIZATION\(posts index_posts_on_author_id\) \*/}) do
         posts = Post.optimizer_hints("/*+ NO_RANGE_OPTIMIZATION(posts index_posts_on_author_id) */")
diff --git a/activerecord/test/cases/adapters/postgresql/optimizer_hints_test.rb b/activerecord/test/cases/adapters/postgresql/optimizer_hints_test.rb
index 5e4bf232e1..5b9f5e0832 100644
--- a/activerecord/test/cases/adapters/postgresql/optimizer_hints_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/optimizer_hints_test.rb
@@ -19,6 +19,14 @@ if supports_optimizer_hints?
       end
     end
 
+    def test_optimizer_hints_with_count_subquery
+      assert_sql(%r{\ASELECT /\*\+ SeqScan\(posts\) \*/}) do
+        posts = Post.optimizer_hints("SeqScan(posts)")
+        posts = posts.select(:id).where(author_id: [0, 1]).limit(5)
+        assert_equal 5, posts.count
+      end
+    end
+
     def test_optimizer_hints_is_sanitized
       assert_sql(%r{\ASELECT /\*\+ SeqScan\(posts\) \*/}) do
         posts = Post.optimizer_hints("/*+ SeqScan(posts) */")